Figure 3(c) shows the temperature-dependent resistance of sample S3 in the warming and cooling cycles. A sharp drop of resistance below 180 K is clearly observed, suggesting the occurrence of superconductivity within the ternary La-Ce-H system. The zero-resistance state is achieved at lower temperatures. The broad superconducting transition is attributed to the various anisotropic stress inside the DAC. The \(T_c\)  value of 175\(\pm \) 2 K is defined from the temperature derivative of the resistance (dR/dT) in the warming cycle as shown in Fig. 3(d). The obtained \(T_c\)  of 175\(\pm \) 2 K in present sample shows consistency to the \(T_c\)  values in the recently discovered P6\(_3\) /mmc-La\(_{0.5}\) Ce\(_{0.5}\) H\(_{9}\) , P6\(_3\) /mmc-(La,Ce)H\(_{9-10}\)  and Fmm-(La,Ce)H\(_{9-10}\)  [1]}, [2]}. In addition, PtH with hcp structure exhibits superconductivity with a \(T_c\)  of 7 K at 30 GPa [3]}. However, \(T_c\)  of PtH was reported to decrease upon compression and becomes undetectable at the pressure range. Meanwhile, Imm-LaH\(_6\)  was reported to stabilize kinetically with an estimated \(T_c\)  of 176 K at 180 GPa [4]}, the superconducting order may be suppressed for the strongly correlated interactions of 4f electrons. Therefore, we attribute the present superconducting phase to Fmm-La\(_{0.5}\) Ce\(_{0.5}\) H\(_{10}\) .
<FIGURE>